java - 删除列表中的重复记录

Question

您好，在开发我的一个 Web 应用程序时，我基于执行的 sql 查询将用户信息存储到 ArrayList 中，它包含重复对象如何删除列表中的重复对象，我已经尝试了一些方法，但它仍然无法正常工作。这是我的代码纠正我错误的地方

      public ArrayList loadData() throws ClassNotFoundException, SQLException {
    ArrayList userList = new ArrayList();
    String url = "";
    String dbName = "";
    String userName = "";
    String password = "";
    Connection con = null;
    Class.forName("org.apache.derby.jdbc.ClientDriver");
    con = DriverManager.getConnection(url + dbName, userName, password);
    PreparedStatement ps = null;
    try {
        String name;
        String fatherName;
        int Id;
        String filePath;
        int age;
        String address;
        String query = "SELECT NAME,FATHERNAME,AGE,ADDRESS,ID,FILEPATH FROM USER_INFORMATION ,USER_PHOTO WHERE ID=USER_ID";
        ps = con.prepareStatement(query);
        ResultSet rs = ps.executeQuery();
        while (rs.next()) {
            name = rs.getString(1);
            fatherName = rs.getString(2);
            age = rs.getInt(3);
            address = rs.getString(4);
            Id = rs.getInt(5);
            filePath=rs.getString(6);
           /* if(flag)
            {
                prev=Id;
                flag=false;
            }
            else if(Id==prev)
            {
                TEMP=TEMP+";"+filePath;
            }*/
            //PhotoList = PhotoList(Id, con);
            UserData list = new UserData();
            list.setName(name);
            list.setFatherName(fatherName);
            list.setAge(age);
            list.setAddress(address);
            list.setId(Id);
   //       list.setFilePath(filePath);
            userList.add(list);
        }
        ps.close();
        con.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    ArrayList al = new ArrayList();
    HashSet hs = new HashSet();
    hs.addAll(userList);
    al.clear();
    al.addAll(hs);
    return al;
}

我的 Bean 类内容是

    public class UserData {

private String name;
private String fatherName;
private int Id;
//private String filePath;
private int age;
private String address;
public UserData()
{

}

public UserData(String name, String fatherName,int Id, int age,String address)
{
    this.name = name;
    this.fatherName = fatherName;
    this.Id = Id;
    //this.filePath=filePath;
    this.age=age;
    this.address=address;
}
//GETTER AND SETTER..

Answer 1

总体思路:使用Set , 不是 List .但是你必须覆盖类的散列和等于。